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Mild hybrid aims to create long-haul fuel savings

HANNOVER, DE. Calling it a mild hybrid, Eaton is working on the development of an integrated system that bolts on to a heavy-duty transmission PTO replacing belt-driven accessories with electrically driven air conditioner compressor, alternator, starter and invertor to capture and store electric power. The 48-volt system should offer significant fuel savings by removing accessory parasitic power drains while also providing engine-off AC when drivers are off duty. The company introduced the new mild hybrid system, which is still in the prototype phase, at the 2018 IAA commercial vehicle show.

The single transmission-mounted package replaces a traditional starter motor with an electric motor designed for automatic engine stop/start functionality. When paired with Eaton’s 12-speed automated HD transmission, it can generate electric power for storage in batteries when a truck enters neutral coast modes. That stored power can also run an integrated AC compressor, providing cooling when the engine is off, either when coasting or parked.

Fuel savings estimates for the hybrid range from 3% to 7%, according to Matt Nolan, global product strategy manager for Eaton’s eMobility division. The prototype could move to U.S. production by 2021, he said. The 48-volt transmission-mounted system can also provide 24- and 12-volt power for vehicle electric loads, and reduces overall weight up to 50 lbs. by reducing or eliminating cables and harnesses, according to Eaton.

In other IAA news, Eaton also introduced a 4-speed transmission for electric medium-duty trucks and buses. Unlike single- and 2-speed drives commonly used in electric commercial vehicle applications, the new 4-speed is intended to offer both high efficiency at top speeds and increased torque for launch and low speeds. With a torque capacity of 885 lbs.-ft, it does not have a clutch and uses gearing optimized for electric motor performance.

Schedule to enter production later this year, the 4-speed transmission has shown a 20 to 30% efficiency improvement over single-speed drives and a 10 to 15% improvement over 2-speed transmissions, according to Eaton. Truck applications include medium-duty refuse collection, utility trucks and other medium-duty commercial vehicles with GVWs up to 18 tons, the company said at the European introduction.